We are forced to lock our vehicles, residences and places of business to deny access to criminals. When we approach these locks with key in hand, we, too, are vulnerable to personal attack by these criminals. Defensive experts advise us to ward off an attack by stabbing with whatever is at hand, even a key. This is not very effective. We can carry a weapon in the other hand, but this leaves no hand for packages, or door opening, and the user must find storage for the weapon when not in use.